Found my 915 noise source, lots of questions
 

Finally found the reasons for my 915 noise.

1. The inner surface of the input shaft roller bearing is badly pitted. It's hard to see but it is the OD of the inner race.
http://forums.pelicanparts.com/uploa...1242528852.jpg

2. The reverse idler gear surface is badly pitted.
http://forums.pelicanparts.com/uploa...1242528936.jpg

Question 1: replacing the idler shaft is obvious, but should I also replace the surface bearing (not needle bearing) that goes up against that pitted surface?

Question 2: The 2 needle bearings cages inside the reverse gear fall apart very easily, are they bad? I did not see any scoring on the shaft or on the bearings so are they still good?
http://forums.pelicanparts.com/uploa...1242529097.jpg

Question 3: is this input side reverse gear good, or bad?
http://forums.pelicanparts.com/uploa...1242529197.jpg

Question 4. Are these spacers still usable with the imperfect edges?
http://forums.pelicanparts.com/uploa...1242529264.jpg

Question 5: is this 1/2 slider gear usable?
http://forums.pelicanparts.com/uploa...1242529336.jpg

Question 6: is this 5/R slider gear usable?

http://forums.pelicanparts.com/uploa...1242529395.jpg

more questions
 

Question 7, The lower bearing outter race on the case can be spun by hand. Is that supposed to be that way? Or, do I need to replace the race and the bearing?
http://forums.pelicanparts.com/uploa...1242529580.jpg

Question 8: This first gear on the input shaft, is that still good?
http://forums.pelicanparts.com/uploa...1242529639.jpg

Question 9: is this input side second gear still good?
http://forums.pelicanparts.com/uploa...1242529690.jpg

Question 10: Gear 1 input side is slightlhy higher 1/16 inch than Gear 1 on the output side, is that normal?
http://forums.pelicanparts.com/uploa...1242529778.jpg

Question 11: notice the input shaft with gears 1/2/3/4 on it, I am not planning on taking them apart because I have no way to put the nut back on. I have inspected the surfaces, the gears, the slider, the synchros, and will clean them before assembly. Is that Ok by most standards?
http://forums.pelicanparts.com/uploa...1242529942.jpg

Question 12: how do I press on the gears on the output shaft without a press?

http://forums.pelicanparts.com/uploa...1242530016.jpg

Okay. I'll have a go... But hopefully Grady, Peter Z or JWW will chime in and correct me :)

I'm just going through this now...

1. Replace roller bearing
1a. Replace idler AND bearing
2. Not sure
3. Looks fine to me
4. Reuse
5. You should replace synchro bands and slider whilst you have it apart (is it a later or earlier box? Because there is a difference in the 1st gear synchro and slider).
6. Looks okay, but how are the reverse teeth?
7. Spinning race IS a PROBLEM - normally requires some machine work and pressing in a 'speedy sleeve'. There are some bearing retaining products from Loctite, but it's a call a professional would have to make.
8. Looks fine
9. Appears fine in the photo
10. They should be even
11. DANGER Will Robinson. You really should disassemble and review the components. Unless you have recorded proof of a recent rebuild, you really should change the 1/2 synchro bands, brakes and dog teeth - 1/2 slider should also be replaced at the same time.
12. To get everything off - Gravity. Heat the four-point bearing race (the small ring holding the roller bearing above it), and then smack the whole thing down on a piece of steel/aluminum plate (I know this sounds brutal, but it is what the pros do!).

To get the gears back on, mine slid most of the way on and then I did the reverse of getting them off...

Like I said, a few of the real experts will chime if for you I'm sure. But I am almost positive they will suggest that you completely R&R the mainshaft. There are quite a few good threads on making tools to do the job without using factory tools (I used an old clutch plate in a vice and a big @ss shifter to undo the 41mm nut - getting it back on involved a home-made 41mm crow foot and torque wrench with additional math to calculate the offset caused by using a crow foot).

I think a gearbox is truly one of those components where you need to be thinking "while I'm in there..."

Good luck

In regards to your spun bearing you can check out my rebuild here:

http://forums.pelicanparts.com/porsche-911-technical-forum/458853-getting-ready-915-rebuild-its-my-turn.html?highlight=turn+915

And here:

http://forums.pelicanparts.com/porsche-911-technical-forum/469037-915-rebuild-part-ii-time-assembly.html?highlight=turn+915

I agree with Fishcop.

I think #2 is okay.

The loose bearing race clearance should be measured. Peter Z. (much smarter than me) will tell you to get the machining mod done I think. If it is only a small gap, say, 0.0005" I would loctite it. Others here will disagree. If Peter disagrees with me, take his advice over mine. :)

You need to finish the tear down. If you have no other option you can grab the un-used part of the shaft (NOT the machined surface) in a vice and take the nut off with an adjustable wrench. I do not recommend that method, but it is preferable to just assuming the internals are all good. There are several threads showing the proper way to do it. If you can not get access to the right re-torquing tools mark the nut rotation with a scriber before you remove it, and then re-set it to the same point when you are done. I DO NOT RECOMMEND this method, but it is better than leaving the shaft assembled and hoping everything is good. Since you are in California, not exactly the middle of nowhere, you would be better off to pay someone to help you, or get a local Pelican to lend you some tools.

To get everything off you can pound it on the floor hitting the hard end of the shaft on a steel or aluminum plate. Sounds crazy but John Walker does it that way. I did it last week, it is pretty easy. Post pictures of the synchros and the dog teeth.

If you do not have a press get your stuff organized and go to a machine shop and have them press it for you. Should only take 15 minutes. Worth the time/effort in my opinion. (I stack everything in order on a piece of wooden dowel, then just slide the pieces off and press them on in that order)

P.S. Nice pictures. I can tell from your 'organizational skills' that you will be able to do this.

Screw it, I am welding up a socket for the main shaft nut.

Looking for a thow away clutch plate for a holder.

Those pictures were made with Nikon $tuff, so they better be good.

Wise decision. Post pics and hopefully Peter Z will chime in. We are amateurs, he's a pro.

So far, no taker on my beg for a throw away clutch disc. Do any of you want to lend me yours?

Yelcab, you're in San Carlos... I've got a funny feeling that's where Wevo is located :)

About the spun bearing race.

It moves in and out about 0.050". With my hand, I can spin it in its place with the present lubrication but it does not easily slide out of the hole. With a small slide hammer, it came out eventually.

I measure the hole with a boring gauge and the bearing race with a micrometer and the hole is 0.001 to 0.002" larger than the bearing race ... and once it came out, it is not possible to just slide the bearing race back on dry.

My guess is it is supposed to be interference fit and that is too loose.

Given that situation, any recommendation? Somebody mentioned Wevo ... looked at their web site and saw the retainer plate. Will that work in conjunction with locite?

wow John, that is almost $1,000 for a mod. I think I will look for a different solution first.

#7.....was the cause of my 2nd gear explosion. Get the bearing retainer plate from WEVO or GT/Guard transmission. I machined the case, pressed in a sleeve and replaced the bearing.

DO NOT Loctite it....

Yep. It is the Rolls Royce fix...

I think you need it machined somehow somewhere. Loctite will not be permanent, that is too much clearance.

Good info!

OK Mikez, what machine shop did you use? Care to pass on the info?

Secondly, the good book Bentley does not show a disassembly sequence for the transaxle. Can someone post a few simple steps and things to look out for so that I can assemble the tranxale back together and not changing the shim pack, and not having to measure backlash etc...

Loose bearing race - Engine Machine Service (310) 641-7019 - talk with Bill or Dick. Take the housing (they'll clean it), the side cover and a new P/S bearing outer race. They'll machine an insert, install it, and install the race.

Regarding your gears, a camera just can't replace eyes. If there is any tooth root wear (through the hardened surface, usually found on the smaller gear of each gear set) that gear set is a throw-away. (Dog teeth don't matter, they can be replaced). Root wear is most common on 1st, 2nd & 3rd - in that order.

Reverse idler pin - throw away. So are the bearings. Look carefully at the idler gear, where it contacted the flat bearing. There is a good chance that it has wear similar to that on the pin, if it does the idler is also a throw-away.

Aase Brothers.....one of them has a machine shop in Orange County, CA. He did it for me while I waited.

BTW, what year 915 is this? I have an early 915 that has the retainer already in it and was just freshened up. I rebuilt it for a project that didn't materialize due to the economy taking a dive.

Email me, 356 at cox.net if interested. I'm in it cheaper than you'll be with the issues you have.....and it's ready to go. You shouled be able to recover some costs by selling the gear sets. The 7:31 Ring and Pinion is fun even with a high hp motor.....easy swap for higher gearing if that's what you have now.

Thanks Pete

How about a dissambly sequence for the transaxle. Anything specific to keep in mind so that it all comes back with the same backlash and shim pack ?

Many years ago, I had a shop replace a cracked transaxlehousing on a different 915, it broke 3 times after that. My guess is they never did the shim pack right. I don't want that for this time.

All that you have to do is:

1. Remove both diff carrier bearing races (mark them somehow if you're going to re-use them),
2. Remove the side cover o-ring,
3. Remove both axle flange seals (housing & cover),
4. Remove the TOB guide tube,
5. Remove the M/S bearing outer race,
6. Remove all of the clutch release parts (shaft, fork, etc.) but don't remove the black, plastic tube.

No need to send the old P/S bearing race, all that EMS needs is the race for the new bearing. Do not remove the clamping plate studs.

That's about it. Put your pinion depth shims together and secure them with a ty-rap. Do not remove the diff carrier bearings unless you're going to replace them. If you replace them do one at a time so you can't mix up the pre-load shims, and be prepared to check/set bearing pre-load when you're ready for assembly.

Peter, how can I tell if the gears have worn through the hardened surface? Is it polished, or rough? does it have wear patterns? Does it ???

You will generally see pitting. If it's really bad the pits start to connect into a straight line. It's most commonly down near the root of the tooth on the running surface. You need to look at every tooth on every gear in addition to the ring and pinion. Sometimes it will only be on a single tooth, but if a single tooth breaks off, it will still usually do catastrophic damage.

Also, regarding your case issues, we've developed another methodology of repairing it other than the shim method. We use oversize bearing races. We take the case and machine it round (it is currently out of round, which is why it hangs at some points and is loose at others when you spin the race). Then we install the oversize bearing race and it's as good as new.

Bearing plates like Guard sells are only good as a preventative. There's a number of shops that will tell you it's a fix for the case bearing problem. It is not. It can reduce the wear and tear and prevent the problem from happening, but once it's happened it's too late. I only mention this because while it hasn't been said in this thread, if you start making phone calls, certain shops will try to sell you the plate as a fix and convince you to peen the case or loctite it, along with the plate. That's a bad idea.

Good info from Matt. My top pic shows the beginning of root wear/tooth failure on the bottom/middle tooth. The middle picture shows extreme wear, and the lower picture (poor) shows the flash hitting and bouncing off of root wear. Think of root wear as a cavity in one of your teeth - it starts small, then turns ugly.http://forums.pelicanparts.com/uploa...1242741917.jpg
http://forums.pelicanparts.com/uploa...1242741994.jpg
http://forums.pelicanparts.com/uploa...1242742020.jpg

Peter

Sorry for being dense, you mean the fuzziness in the circle? that is root wear? Or the little pits all over the surface of the gear tooth?

http://forums.pelicanparts.com/uploa...1242746495.jpg

I'm not able to draw circles/arrows, etc. on pictures but here are a couple of new pics... hopefully they will show you what you need to know!http://forums.pelicanparts.com/uploa...1242752524.jpg

oops! Hit the wrong button... here's one more.http://forums.pelicanparts.com/uploa...1242752661.jpg

Thanks, got it. I don't have any of that, thank God. The only wear that looks like that is at the roller bearing on the main shaft. The hard to see picture at the very top of this post shows that. And then the idler shaft. They are both junk.

Your pictures of the second gear set look like they have been through acid.

Nice pictures. Street car or race car or in between? Looks like you are on the right track. I have a clutch disk if you still need one, and a need to visit RWC/San Carlos area this week.

If you need to do something about the main case or final drive housing in terms of machining, perhaps WEVO have what you need. I bought their main case a few years ago. I also have their shifter and coupler and retaining plate. They make excellent products and also do exceptional work. Cannot recommend them highly enough.

Mike, I have a clutch disc coming, so thank you.

I talked to Wevo and they charge $1000 for the case reinforcement. That is a little more than I want to spend for this weekend toy. I drive it hard but I don't race it or anything.

Case reinforcement? Is that the bearing shell removal and pressing in a sleeve? I think I paid $300 with Aase.

Matt said,

I had looked into having oversize bearing races made but it's very specialized machining and is cost prohibitive.

Just wondering Matt where you found oversize bearing races? Are they from a specific application and, if so, which one?

Thanks

From a 3.2 Carrera with about 200K miles. The trans had been opened, I have a hunch more than once, and a real doofus had done some horrible things in there. That said, it's one of the worst gears I've ever seen that didn't break.

I know that you guys hate these words but it's a "trade secret". My builder, who used to be PHII's builder, came up with this solution about 10 years ago. He's always been very hush hush about it and won't let me tell the exact details of how we do it.

But I'm working on him and he seems to be wearing down. I might be cleared to talk about it pretty shortly. I'm trying to convince him that the community will be better served by more people knowing how to make this repair using what we consider a better way than the shim method. It's not always about making money. However it does require some specialized equipment to do it, and we do the whole process in house. We've got our own CNC mill, among other things.

I do sincerely apologize for not being able to spill the beans. I try to keep business clear of my posts here and just participate on technical aspects. I almost didn't say anything at all, but thought the OP would be better served by knowing all options and since it doesn't compete with Wayne's business I felt it was ok to say something.

Aase brothers are out of the bidness (so the song goes).

Matt,

In my mind, using a race with an oversized O/D makes a bit more sense than inserting a shim/sleeve if for no other reason than it doesn't reduce the amount of remaining aluminum casting between the input & pinion shaft bearings as much. Plus, pressing one thin metal shim inside another just doesn't seem like its a permanent solution...maybe I'm wrong.

Based on the research I've done thus far, it's probably fairly safe to assume your builder is not making the races or having them made. They are probably from another existing automotive application.

Perhaps some day soon you'll get the green light to share the "trade secret."

Thanks for your response.

Matt, at the risk of taking you somewhere you don't want to go :).... but my guess would be that a plating technique is used to enlarge the outside only dimension of the bearing race (hard chrome?) as the size increase needed is minimal. But as you suggest the, specialist machining required to bring the case back to round would not be for the average home machinist!

Cheers

I don't think hard chroming can build up 0.002" evenly. A few tenths is the limit I think. Beyond that you would need to go oversize and then grind it.

And there is no guarantee that the bore is round, it likely isn't, so it still needs to be machined...

I have read in other threads about hard chroming the OEM race to make it slightly bigger... (temporary fix at best IMO)

To be honest I'm a bit dubious about all fixes except for the WEVO option.

After all the main reason (but not the only one) the PS shaft bearing becomes shagged out is because of the amount
of material between the PS and input shaft bearings.

Porsche fixed the problem by installing a smaller bearing on the input shaft...
Result = More alloy between the two bearings which fixes the problem. (credit to Peter Z about this subject in many different posts)

So what we need is for someone to develop a solution the mimics the Porsche solution... And that already exists ~ The WEVO option
But could it be done at a more reasonable price?

A suggestion for a permanent fix...
1. Machine and install a steel reinforcing ring on the PS shaft bearing. (most recommended fix)
2. Machine and weld in an alloy ring in the "input shaft bearing area that fits the smaller bearing from the later 915.

Funny thing is it starting to sounds like a lesser version of the WEVO fix.

Something to consider which hasn't been mentioned is the tendency of the lower five studs that hold the PS bearings
retaining plate to become slightly loose. These studs are constantly submerged in tranny oil and the locking compounds
Porsche used 20+ years ago are not the same as the ones available to us today.

I would check all 9 studs before rebuilding the trans.

It's easy to do... Lock two nuts on the lowest stud and check how much force it takes to rotate that stud... Lock two nuts on the upper most stud and compare the two.

If they are loose... Re secure them. Remove studs, Clean the stud hole and stud with acrylic thinners,
Reinstall the the studs using "Loktite Red" to re secure (apologies for being obvious in advance)

Just puttin' in out there :D